Dive Bombing: USN vs USAAF/USAF

[rickshaw]

One bird thhat seems to have been ignored was the A31/35 Vengeance. While it served with the Army in some minimal capacity, other air arms put it to good use. How did the Vengenace fair when compared with the other aircraft mentioned here?

Smith maintains that the Vengeance was intended to be the Allies' answer to the Stuka divebomber.  However, as the war developed, distrust of a pure divebomber which was already high amongst the Allied commanders prevented it being used very much.  The RAF used it in Burma, the RAAF in New Guinea but in both cases the Vengeances were withdrawn before they could really show their stuff.  The USAAC prevented their squadrons from serving overseas.  The RAAF converted it's squadrons to flying Liberators in mid-1944, I'm unsure what happened to the RAF squadrons.  It was more a case that diveboming fell out of favour after the Battle of Britain and fighter-bombers pretty well replaced the divebombers in the dedicated attack role and were considered more versatile.

[KJ_Lesnick]

Everybody

I'm curious about one particular detail about this aircraft: The scoops

http://www.airwar.ru/image/idop/aww2/a41/a41-1.jpg
http://www.nationalmuseum.af.mil/shared/media/photodb/photos/051122-F-1234P-058.jpg
http://www.airwar.ru/image/idop/aww2/a41/a41-3.jpg

The aircraft has one on the top, one on the bottom: Generally an inline engine needs a radiator for the engine, oil-coolers, and if intercooling/after-cooling is used, a radiator for this purpose.

So, which is the oil-cooler, and which is the intercooler radiator?


Rickshaw

Smith maintains that the Vengeance was intended to be the Allies' answer to the Stuka divebomber.  However, as the war developed, distrust of a pure divebomber which was already high amongst the Allied commanders prevented it being used very much.  The RAF used it in Burma, the RAAF in New Guinea but in both cases the Vengeances were withdrawn before they could really show their stuff.

I'm curious about something: Could the internal bomb-bay be used for dive-bombing, or did it require the external pylons for this?

[rickshaw]

The internal bomb bay was intended for dive bombing, Kendra/Robynn.  I'd recommend purchasing/borrowing any of Smith's books on dive bombers/bombing.  They are a mine of information on the topic.

[NARSES2]

I'm unsure what happened to the RAF squadrons.  It was more a case that diveboming fell out of favour after the Battle of Britain and fighter-bombers pretty well replaced the divebombers in the dedicated attack role and were considered more versatile.

Last RAF use in Burma was 84 Sqd July 1944. 110 Sqd was transferred to West Africa and used them until Dec 1944 in chemical warfare experiments.

[dogsbody]

Upper intake is for engine air ( carburation ).
Lower intake is for the oil cooler.


Chris

[wuzak]

The aircraft has one on the top, one on the bottom: Generally an inline engine needs a radiator for the engine, oil-coolers, and if intercooling/after-cooling is used, a radiator for this purpose.

So, which is the oil-cooler, and which is the intercooler radiator?

The XA-41 had a single stage R-4360. This being air cooled didn't need an engine radiator, and being single stage and not using a turbo it did not have need for an intercooler.

I defer to dogsbody as to which scoop does what.

[KJ_Lesnick]

rickshaw

The internal bomb bay was intended for dive bombing, Kendra/Robynn.

I just remember the SB2C having an extendable bomb-crutch for improved dive-bombing performance due to it's bomb-bay


dogsbody

Upper intake is for engine air ( carburation ). Lower intake is for the oil cooler.

I'm curious if you have the means to answer the following

1. Why did the F4U have almost no discernible intake where as this airplane and the A-1 did?
2. Why did the A-1 have such a small intake in comparison
3. What kind of supercharging if applicable does this plane use
4. What kind of supercharging did the AD-1/A-1 have?

[wuzak]

Upper intake is for engine air ( carburation ). Lower intake is for the oil cooler.

I'm curious if you have the means to answer the following

1. Why did the F4U have almost no discernible intake where as this airplane and the A-1 did?
2. Why did the A-1 have such a small intake in comparison
3. What kind of supercharging if applicable does this plane use
4. What kind of supercharging did the AD-1/A-1 have?

1. The F4U's engine intakes were in the leading edge of the wing. I believe the oil coolers were there too.

The F4U-5 with the "sidewinder" R-2800-32W had cheek intakes for the engine.

http://www.trahern.net/34.jpg
https://s-media-cache-ak0.pinimg.com/736x/d5/c1/04/d5c104086f6284238afcc4c62e28813e.jpg

The FG-1 had a top mounted engine intake.

https://upload.wikimedia.org/wikipedia/commons/2/24/Goodyear_F2G-1D_Corsair_at_NAS_Patuxent_River_1947.jpg

2. The A-1/AD-1 had a smaller, less powerful, engine. The R-3350 of ~2800hp vs the R-4360 of ~3500hp.

3. The A-41 used a single stage two speed integral supercharger for its R-4360.

4. The A-1/AD-1 used a single stage two speed integral supercharger for its R-3350..

For 3 and 4 I am not certain that they are two speed, but they are definitely single stage.

[KJ_Lesnick]

Wuzak

Thank you for your reply, your knowledge on this forum is of extreme value

1. The F4U's engine intakes were in the leading edge of the wing. I believe the oil coolers were there too.

Would wing-root mounted intakes be good, bad, neutral for a dive bomber?

The F4U-5 with the "sidewinder" R-2800-32W had cheek intakes for the engine.

Could any of the following set-ups be adopted (with the aim of producing a cleaner layout)

• Place the intake in the oil-cooler duct, the air goes into the intake and cooler cold; the intake air feeds the engine, and the rest cools the intake?
  
• Flatten the oil-cooler a bit and widen it so that the air-intakes parallel the oil-cooler and effectively produce clean shape along the underside?
  

.

The FG-1 had a top mounted engine intake.

https://upload.wikimedia.org/wikipedia/commons/2/24/Goodyear_F2G-1D_Corsair_at_NAS_Patuxent_River_1947.jpg

This arrangement used an R-4360: It's intake shape though basically looked more like the A-1 Skyraider in arrangement.  I'm curious if this arrangement is better than the intake used on the XA-41?  Is there any rule of thumbs for this sort of thing?

2. The A-1/AD-1 had a smaller, less powerful, engine. The R-3350 of ~2800hp vs the R-4360 of ~3500hp.

True enough, but the F2G-1D had a similar intake setup...

3. The A-41 used a single stage two speed integral supercharger for its R-4360.

4. The A-1/AD-1 used a single stage two speed integral supercharger for its R-3350..

For 3 and 4 I am not certain that they are two speed, but they are definitely single stage.

Understood: Where would one look as this is fairly obscure?

While I'm at it: Why is the range of the XA-41 and AD-1 so different?

• XA-41: 800-950 miles with 1,000 lbs
  
• AD-1: 1,940 miles with 2,000 lbs
  

[wuzak]

1. The F4U's engine intakes were in the leading edge of the wing. I believe the oil coolers were there too.

Would wing-root mounted intakes be good, bad, neutral for a dive bomber?

It would depend on the engine, its induction setup, its position relative to the wing, etc. In principle, it would be possible, but turning air through ducts will lose some of the ram effect.

And example is that when Hooker started at Rolls-Royce he modified the intake elbow of the Merlin and gained several thousand feet of FTH.

The F4U-5 with the "sidewinder" R-2800-32W had cheek intakes for the engine.

Could any of the following set-ups be adopted (with the aim of producing a cleaner layout)

• Place the intake in the oil-cooler duct, the air goes into the intake and cooler cold; the intake air feeds the engine, and the rest cools the intake?
  
• Flatten the oil-cooler a bit and widen it so that the air-intakes parallel the oil-cooler and effectively produce clean shape along the underside?
  

The first point, sure it can be done. But it depends on the engine architecture. The second point, I'm not sure what you are saying. Can you do a hand sketch?

The FG-1 had a top mounted engine intake.

https://upload.wikimedia.org/wikipedia/commons/2/24/Goodyear_F2G-1D_Corsair_at_NAS_Patuxent_River_1947.jpg

This arrangement used an R-4360: It's intake shape though basically looked more like the A-1 Skyraider in arrangement.  I'm curious if this arrangement is better than the intake used on the XA-41?  Is there any rule of thumbs for this sort of thing?

It's down to detail design. I think, in general, you want the shortest duct possible. But being as far back as on the F2G you may have issues with boundary layers on the cowl, which will required boundary layer splitters, or similar. The longer duct to the nose avoids this issue.

2. The A-1/AD-1 had a smaller, less powerful, engine. The R-3350 of ~2800hp vs the R-4360 of ~3500hp.

True enough, but the F2G-1D had a similar intake setup...

I'd suggest that the F2G intake is larger than the A-1's.

2. The A-1/AD-1 had a smaller, less powerful, engine. The R-3350 of ~2800hp vs the R-4360 of ~3500hp.

True enough, but the F2G-1D had a similar intake setup...

3. The A-41 used a single stage two speed integral supercharger for its R-4360.

4. The A-1/AD-1 used a single stage two speed integral supercharger for its R-3350..

For 3 and 4 I am not certain that they are two speed, but they are definitely single stage.

Understood: Where would one look as this is fairly obscure?

Get a book about the engines, or one that deals with several types but has details on the sub-types. Check the engine type listed on the aircraft's data against that.

I have an R-4360 book, but it is currently in storage. I do have a book that may have some details:
http://www.amazon.com/Allied-Aircraft-Piston-Engines-World/dp/1560916559

While I'm at it: Why is the range of the XA-41 and AD-1 so different?

• XA-41: 800-950 miles with 1,000 lbs
  
• AD-1: 1,940 miles with 2,000 lbs
  

There is little doubt that the R-4360 is a thirstier engine.

Then the other factors are fuel capacity, weight, aerodynamic efficiency, operating altitude, etc.

[KJ_Lesnick]

Wuzak

It would depend on the engine, its induction setup, its position relative to the wing, etc. In principle, it would be possible, but turning air through ducts will lose some of the ram effect.

And example is that when Hooker started at Rolls-Royce he modified the intake elbow of the Merlin and gained several thousand feet of FTH.

And ram effect effectively produces a supercharging effect all it's own so maximizing it would improve, in essence, the effectiveness of the supercharger and, by extension, the critical altitude of the engine?

The first point, sure it can be done. But it depends on the engine architecture.

I know almost nothing of the R-4360 architecture other than it has four rows of cylinders in a semi-helical set-up with the front cylinder running hotter than the second third and fourth.  If you have any information on the engine architecture, I could use it.

The second point, I'm not sure what you are saying. Can you do a hand sketch?

I'll see what I can do... It might take a few attempts.

It's down to detail design. I think, in general, you want the shortest duct possible. But being as far back as on the F2G you may have issues with boundary layers on the cowl, which will required boundary layer splitters, or similar. The longer duct to the nose avoids this issue.

So the shortest duct possible favors the AD/F2G in theory, the best interaction between the boundary layers favors the A-41 in theory?

I'd suggest that the F2G intake is larger than the A-1's.

True but it's still shaped more like the A-1's in shape than the A-41...

There is little doubt that the R-4360 is a thirstier engine.

I'll check the SFC figures on the R-4360 and R-3350

Then the other factors are fuel capacity, weight, aerodynamic efficiency, operating altitude, etc.

I'm not sure how much fuel each carried... I've been making guesses based on trying to estimate ammo weight and the plane's loaded weight, and taking away fuel: I'm not sure how much the ammo used weighs (belt links and stuff)

[wuzak]

Wuzak

It would depend on the engine, its induction setup, its position relative to the wing, etc. In principle, it would be possible, but turning air through ducts will lose some of the ram effect.

And example is that when Hooker started at Rolls-Royce he modified the intake elbow of the Merlin and gained several thousand feet of FTH.

And ram effect effectively produces a supercharging effect all it's own so maximizing it would improve, in essence, the effectiveness of the supercharger and, by extension, the critical altitude of the engine?

Yes, the ram effect improves the critical altitude of the engine, by as much as a few thousand feet.

Engine critical altitudes (FTH in British parlance) are often denoted as with or without ram. Mostly they are test bench figures, so are without ram.

[KJ_Lesnick]

Wuzak

Yes, the ram effect improves the critical altitude of the engine, by as much as a few thousand feet.

Speed would play a role too right?

I'll draw the sketch

[wuzak]

Wuzak

Yes, the ram effect improves the critical altitude of the engine, by as much as a few thousand feet.

Speed would play a role too right?

I'll draw the sketch

Yes, the ram effect is linked to speed.

[KJ_Lesnick]

This is the best I can do... I know it sucks


The three arrows point to the scoops, the left and right are intakes; the ventral one is the oil-cooler.  I circled the ventral area to distinguish that scoop from the others